Recently, the characteristics of polyester fibers have been remarkably improved. Especially, feeling, touch and drape of polyester fabrics have been improved to a level comparable to that of natural fibers (for example, Japanese Examined Patent Publication No. 61-36099). Nevertheless, appearance, particularly the color depth, of the dyed polyester fabrics is not attractive as compared with those of fabrics of natural fibers such as silk and wool. It is therefore usual that consumers' interest is not excited at the first sight, even though the feeling and other characteristics are improved.
Proposals of improving the dyeability and other dyeing properties have heretofore been made, which include, for example, the copolymerization of a specific comonomer to effect relaxation of the fibrous structure (Japanese Examined Patent Publication No. 63-39686) and the formation of micropores in the surface portion of the fiber to effect diffused reflection (Japanese Examined Patent Publication No. 62-28229). However, dyed polyester fabrics made by these proposals are still not satisfactory in the color depth which term is used in a broad sense in the present specification, i.e., in the color depth with brilliancy, although they are dyed deeply.